Extracorporeal membrane oxygenation (ECMO) is a circulatory assist method that has been developed from the cardiopulmonary bypass technique.1 It is able to provide prolonged life support (from days to weeks) in patients with refractory cardiogenic shock and/or potentially reversible severe respiratory failure refractory to maximum conventional treatment efforts.2–6 Patients with cardiogenic shock who are treated with vasoactive drugs and inotropic agents, often assisted by an intraaortic balloon pump (IABP), suffer a high mortality rate (between 40 and 60%) when such management measures fail.7,8

In relation to venoarterial ECMO (VA-ECMO), few studies on the experience with this technique in Spain can be found in the literature.9–11 No randomized clinical trials have been published in the international literature, though the existing studies report highly variable mortality rates of between 35 and 70% as determined 30 days after implantation, depending on the indication involved.2,3,12–16 This high early mortality rate among VA-ECMO assisted patients is fundamentally attributable to refractory multiorgan failure (MOF).13 However, surviving the initial mechanical support phase does not necessarily imply survival among patients with refractory cardiogenic shock. Although few studies have examined this issue, the in-hospital mortality rate of patients who have been successfully weaned from ECMO remains high (31–59%).17,18

Lastly, analyzing the long-term patient outcome following acute disease is essential in order to justify the investments made. In fact, long-term survival after serious disease has been identified as an important therapeutic endpoint in assessing the efficacy of new therapies.19–21 In this regard, the studies that have analyzed the long-term outcomes in patients requiring VA-ECMO report one-year survival rates of 26–57%.12–14

The present study was carried out to describe the characteristics and analyze the short-term outcome – measured as 30-day survival and in-hospital mortality – and the long-term outcome in patients with refractory cardiogenic shock subjected to VA-ECMO during a period of 6 years in our tertiary hospital with a heart transplantation program.

The study included 46 patients requiring mechanical support with VA-ECMO due to cardiogenic shock between January 2010 and December 2015. During this period, the use of devices of this kind increased gradually in our center (Fig. 2). A peripheral access was used in 39 cases (85%), and a percutaneous approach was adopted in all patients. The indications were: 1) end-stage dilated MCP (13 patients, 28%), including 6 cases of idiopathic dilated MCP, three cases of chronic ischemic MCP, two cases of valvular MCP, and two cases due to anthracycline toxicity; 2) acute myocardial infarction (10 patients, 21%); 3) post-cardiotomy (8 patients, 17%); 4) acute graft failure (7 patients, 15%); 5) non-ischemic acute MCP (6 patients, 13%), and 6) miscellaneous (2 patients, 4%). The patient characteristics are shown in Table 1.

Figure 2.

Number of patients receiving venoarterial extracorporeal membrane oxygenation (VA-ECMO) support in the period 2010–2015. The results are expressed as number (percentage).

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Overall survival and long-term outcome

The overall survival of the global cohort following implantation of VA-ECMO is shown in Fig. 3. Overall survival after 30 days and 12 and 36 months was 59%, 46% and 41%, respectively. Twenty-one patients (46%) were discharged from hospital, with a median follow-up after discharge of 27 months (IQR: 11–49). Ninety-one percent of the patients (19/21) were still alive at last follow-up.

Figure 3.

Overall survival of the global cohort from venoarterial extracorporeal membrane oxygenation (VA-ECMO) implantation. The overall survival rate after 30 days and 12 and 36 months was 59%, 46% and 41%, respectively.

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Fig. 4 shows long-term survival according to the type of indication in those patients who survived the mechanical support phase. A significant finding (log rank: 0.002) was that the least favorable evolution corresponded to the patients in which mechanical support was indicated due to post-infarction refractory cardiogenic shock–with a survival rate at last follow-up of 12.5% (1/8). In contrast, the evolution was more favorable when the indications were acute graft failure and end-stage dilated MCP, with survival rates at last follow-up of 50% (2/4) and 67% (6/9), respectively. The most favorable outcome corresponded to the patients in which mechanical support was indicated due to non-ischemic acute MCP and post-cardiotomy shock: all of these subjects were still alive at the time of VA-ECMO withdrawal.

Figure 4.

Overall survival of the patients following withdrawal of venoarterial extracorporeal membrane oxygenation (VA-ECMO), according to the indication of mechanical support.

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In our center, mechanical support with VA-ECMO is increasingly used for the management of refractory cardiogenic shock. The acute mortality rate of our patients was high, though it must be underscored that the patients who survived beyond admission to hospital had an excellent survival rate of 91% with a median follow-up of 27 months, and with heart function close to normal. These results suggest that circulatory assist of this kind could rescue and offer chances for long-term survival among patients with refractory cardiogenic shock, including some cases characterized by circulatory arrest.

In our series, almost 70% of the patients subjected to VA-ECMO survived the initial phase of mechanical support. On comparing these results with those obtained in other series involving at least 35 patients and likewise including refractory cardiogenic shock of different origins, the data are seen to be similar – with 38–70% of the patients being found to survive the mechanical support phase.12,13,17,18,24 In our study, none of the analyzed variables were of help in predicting successful weaning or the recovery of heart function. However, other studies have correlated echocardiographic,25 laboratory test13,26 and clinical parameters26 to the prediction of weaning. The lack of results in our series may be due to both the limited number of patients involved and the study design, which was not intended to examine this aspect.

With regard to the short-term prognosis, our results are similar to those of other series. The survival rate 30 days after VA-ECMO implantation documented in the literature varies between 30 and 65%, depending on the type of indication2,12,14–16,25 – the figure in our mixed series being 59%. With regard to in-hospital mortality, which in our series was 54%, the literature offers highly variable rates in such patients (35–72%)12,13,16,18 – the main causes of death being refractory MOF, severe neurological damage and infection, in concordance with our own observations.13,18,27 In our opinion, it is more important to analyze patient evolution beyond VA-ECMO, since the withdrawal of mechanical support does not necessarily imply survival. In fact, up to one-third of our patients who survived the mechanical support phase subsequently died in the course of the rest of hospital admission. Few studies have analyzed the evolution of this subgroup of patients, with reported in-hospital mortality rates after the withdrawal of VA-ECMO ranging between 31 and 59%.17,18 In our series, the factors associated to poorer prognosis after withdrawal of mechanical support were a higher SAPS-II score, older age, bleeding of the cannulas and the indication of circulatory assist due to shock following acute myocardial infarction. Specifically, age was the only independent factor associated to greater in-hospital mortality in the multivariate analysis. Previous studies have also related the prognosis of these patients to age,18,28,29 organ damage13,28,29 and the etiology of cardiogenic shock,13,18,28 among other factors.

This is the first Spanish study to report on the long-term evolution of patients assisted with VA-ECMO. Almost one-half of the assisted patients were still alive after one year, and a little over 40% were still alive after three years of follow-up. In comparison, the one-year survival rates found in the literature vary between 26 and 57%, depending on the series.12–14,27 The type of heart disease giving rise to the need for mechanical support was related to long-term survival of the patients after weaning. The outcome of the patients assisted due to post-infarction cardiogenic shock was particularly poor. The survival rate after 30 days in this subgroup of individuals was similar to the 47% recorded in a recent study of 138 patients assisted following acute myocardial infarction.29 However, although 30% underwent heart transplantation, the in-hospital evolution of our patients was poorer than that of another Spanish series reporting an in-hospital survival rate of 72.7% among patients assisted with ECMO due to post-infarction refractory cardiogenic shock.30 In our series, this patient subgroup was small and precluded the drawing of conclusions, though the organ damage caused by initial cardiogenic shock may have played a relevant role in the poor subsequent clinical course. Furthermore, with regard to the rest of the patients, those assisted after acute infarction were older, had a greater incidence of limb ischemia, and were significantly longer on mechanical support. Although our results are unable to provide confirmation, these factors may have influenced the poorer outcome.

The present study has several limitations. Firstly, mention must be made of its retrospective design and the limited number of patients. Nevertheless, the series includes all the VA-ECMO assisted patients in our center, and practically all the study variables were available from the electronic case histories in our center. Secondly, the study involves a population of patients with refractory cardiogenic shock of different origins. Lastly, the single-center nature of the study may complicate extrapolation of the results to other centers. Nevertheless, this is one of the largest Spanish series published to date. Future multicenter studies would be advisable in order to strengthen the clinical relevance of the results and allow a detailed analysis of each of the specific subpopulations of patients that develop cardiogenic shock with an indication of VA-ECMO.

Based on our experience it can be concluded that VA-ECMO is a mechanical support strategy that may be used for the management of patients with cardiogenic shock refractory to conventional therapies. Despite the associated high early mortality rate, long-term survival after the in-hospital phase is good. This type of device not only affords immediate cardiovascular support but can be used as bridging treatment for heart transplantation and – in selected cases – for the implantation of middle-term assist strategies. Patient age and the type of heart disease indicating mechanical support were the factors with the greatest impact upon patient survival in our series.

Renata García-Gigorro was in charge of the literature review, data collection and drafting of the article.

Emilio Renes-Carreño contributed to the study conception and design, and to the analysis and interpretation of the data. He also participated in final critical review of the article.

José Luis Pérez-Vela contributed to data collection and critical review of the article.

Helena Marín-Mateos participated in data collection.

Julián Gutiérrez participated in drafting of the article.

María Angélica Corrés-Peiretti participated in critical review of the article.

Juan Francisco Delgado participated in critical review of the article.

Enrique Pérez de la Sota participated in critical review of the article.

José María Cortina-Romero was in charge of the provision of resources.

Juan Carlos Montejo was responsible for the provision of resources needed to carry out the present study. He likewise gave definitive approval of the presented manuscript version.

The authors declare that they have no conflicts of interest in relation to this study, which has not received financial support.